Sybex usual publishes excellent books. I was dismayed to find this one full of errors in the Q&A sections. While such errors might be acceptable in a 700+ page book on the topic in general, they are *not* acceptable in a book specifically designed to prepare for, and practise the exam.
Folks experienced in Proxy will wonder why Sybex slipped so badly, intermediate users will find it a challenge to spot the errors and correct them, the inexperienced will feel lost, bewildered & frustrated.
Skip this book, wait for the second edition, or use it as a 2nd or 3rd book to expand on another book on the same topic. Don't depend on *this* one for "Test Success".
On the other hand, Sybex has also published their MCSE Proxy Server 2.0 Study Guide, which is excellent.